#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<netdb.h>
#include<stdio.h>
#include<stdlib.h>

int main(int argc, char* argv[])
{
    char *host, **names, **addrs;
    struct hostent *hostinfo;

    if (1 == argc)
    {
        char myname[256];
        gethostname(myname, 255);
        host = myname;
    }
    else
    {
        host = argv[1];
    }

    hostinfo = gethostbyname(host);
    if (!hostinfo)
    {
        fprintf(stderr, "cannot get info fro host:%s\n", host);
        exit(1);
    }

    printf("results for host %s:\n", host);
    printf("Name: %s\n", hostinfo->h_name);
    printf("Aliases: ");
    names = hostinfo->h_aliases;
    while (NULL != *names)
    {
        printf(" %s", *names);
        names++;
    }
    printf("\n");

    if (hostinfo->h_addrtype != AF_INET)
    {
        perror("not an IP host!\n");
        exit(1);
    }
    addrs = hostinfo->h_addr_list;
    while (NULL != *addrs)
    {
        printf(" %s", inet_ntoa(*(struct in_addr*)*addrs));
        addrs++;
    }
    printf("\n");

    exit(0);
}
